1. Field of the invention
The present invention relates to a wireless local area network (WLAN), and more particularly, to a peer power save mode (PPSM) in a tunneled direct link setup (TDLS) wireless network.
2. Description of the Related Art
With development of information communication technologies, a variety of wireless communication technologies have been developed. A wireless LAN (WLAN) is a technology permitting wireless access to Internet in specific service areas such as home or companies or air planes by the use of portable terminals such as a personal digital assistant (PDA), a laptop computer, and a portable multimedia player (PMP) on the basis of a radio frequency technology.
These days, thanks to the increased availability of WLANs, portable terminal users such as laptop computer users are able to perform their tasks with increased mobility. For example, a user can take his laptop computer from his desk into a conference room to attend a meeting and still have access to his local network to retrieve data and have access to the Internet via one or more modems or gateways present on the local network without being tethered by a wired connection. Similarly, business travelers commonly use their portable terminals to gain access to their email accounts, to check if there is any unread email, and to read and send email.
In the initial WLAN technology, a data rate of 1 to 2 Mbps was supported by the use of frequency hopping, spread spectrum, and infrared communication using a frequency of 2.4 GHz. In recent years, with the development of the wireless communication technology, 54 Mbps in maximum can be supported by applying the orthogonal frequency division multiplex (OFDM) technology, etc. to the WLAN. In addition, in the IEEE 802.11 has developed or is developing wireless communication technologies for improvement in quality of service (QoS), compatibility of an access point (AP) protocol, security enhancement, wireless resource measurement, wireless access in vehicular environment, fast roaming, mesh network, inter-working with external networks, wireless network management, and the like.
In the IEEE 802.11, a basic service set (BSS) means a set of stations (STAs) successfully synchronized. A basic service area (BSA) means an area including members of the BSS. The BSA can vary depending on propagation characteristics of a wireless medium and thus the boundary is not clear. The BSS can be basically classified into two kinds of an independent BSS (IBSS) and an infrastructured BSS. The former means a BSS that constitutes a self-contained network and that is not permitted to access a distribution system (DS). The latter means a BSS that includes one or more access points (AP) and a distribution system and that uses the APs in all the communication processes including communications between the stations.
In the initial WLAN communication procedure, the infrastructured BSS required to transmit data necessarily through the AP without permitting the direct transmission of data between non-AP stations (non-AP STAs). In recent years, a direct link setup (DLS) between the non-PA STAs was supported to improve the efficiency of wireless communications. Accordingly, in the BSS supporting the QoS, that is, in the QBSS including QoS STAs (QSTA) and QoS APs (QAP), the non-AP STAs can set up a direct link and directly communicate with each other through the direct link.